COVID's Most Contagious Strain Yet In MA: What To Know About BA.5

MASSACHUSETTS — While Massachusetts has ended most COVID-19 restrictions, the virus remains a factor in daily life. This summer, the state must endure COVID in its most contagious form — the BA.5 subvariant.

The statewide seven-day positive test rate increased from 7.29 percent last week to 7.87 percent Thursday. That's the highest the rate has been since the end of January when the original omicron wave was dying down.

Another key coronavirus metric to rise was the hospitalization rate. The average hospitalizations went from 498.1 last week to 511.3. As of Wednesday, 552 Massachusetts residents were hospitalized with COVID-19.

Read more: MA Town-By-Town COVID: Positivity Rates Rise In 73 Percent Of Towns

Here's what to know about BA.5:

How contagious is BA.5?

BA.5 is the most transmittable COVID variant to date, with greater ability than prior strains to evade prior immunity from COVID infection and vaccination, according to UC Davis Health.

"Even people who have partial immunity from a previous infection or vaccination can still have a breakthrough infection," said Dean Blumberg, chief of pediatric infectious diseases at UC Davis Children's Hospital.

What are the symptoms?

All variants, including BA.5, cause similar COVID symptoms, according to UC Davis Health:

• runny nose
• cough
• sore throat
• fever
• headaches
• muscle pain
• fatigue

New research finds that with each repeat COVID infection — even asymptomatic cases — increases the risk for complications, including the following, UC Davis Health says:

• stroke
• heart attack
• diabetes
• digestive and kidney disorders
• longterm cognitive impairment, including dementia

Each COVID infection also carries some risk of longterm effects — known as post-COVID conditions or long COVID. About 1 in 5 adults who previously had COVID continue to feel post-COVID conditions, according to the CDC.

Long COVID symptoms can include fatigue, rapid heartbeat, chronic pain, muscle weakness, sensory abnormalities and cognitive difficulties.

About 525,878 people in Massachusetts have long COVID, according to estimates from the American Academy of Physical Medicine and Rehabilitation. (In modeling the data, the Academy assumes that 30 percent of non-fatal COVID cases have resulted in long COVID.)

How severe is BA.5?

So far, there is no evidence that BA.5 causes more severe disease than other omicron variants. Some research has pointed to the possibility that BA.5 is overall milder than other strains.

"Statistically, you're going to have a lower risk of having severe illness (if you're vaccinated)," Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, told The Guardian. "That's a really key message."

But lighter severity doesn't necessarily mean lesser societal impact. While research suggests that omicron carries a lower risk of hospitalization than the delta variant that dominated much of last year, the heightened transmissibility of omicron caused COVID hospitalizations and deaths to spike last winter in Massachusetts and the United States.

How much is BA.5 spreading in Massachusetts?

Accurate case totals have been more difficult to determine in recent months because of the greater prevalence of at-home tests, which typically don't get reported to public-health agencies.

On this day last year, Massachusetts had a seven-day average of 280 cases per day, according to federal data. The state has nearly nine times as many reported cases now — a seven-day average of 1,200 per day — and that's not counting infections detected through at-home tests. At the early January peak of the omicron surge, the state reported more than 23,000 average daily cases.

COVID hospitalizations have spiked, going from 498 patients with confirmed or suspected cases June 22 to 552 as of Thursday, according to the state health department. But Massachusetts' death tolls haven't jumped, averaging 31 new deaths in the past week. That's far down from the beginning of the pandemic (278 deaths per day for the week ending April 20, 2020) and the height of last winter's omicron wave (111 deaths per day as of Jan. 25).

Since detecting specific strains isn't a typical component in COVID testing — outside of a sample size to determine the prevalence of variants — it's uncertain how many recent deaths and hospitalizations came from the BA.5 strain or other COVID variants.

But BA.5 took over as Massachusetts' dominant strain in recent weeks and reflects 60 percent of the region's cases for the week ending Saturday, according to the CDC.

How can I protect myself and my family?

Stick to the basics. According to Dr. Gonzalo Bearman, chief of infectious diseases at Virginia Commonwealth University Health, people can help protect themselves and others in the following ways:

"The best way to protect yourself is to continue to be aware of the situation," Bearman said. "If you're not vaccinated, get vaccinated. If you're not boosted and eligible for a booster, get boosted. Continue to wear a mask, and continue to practice social distance, particularly in crowded indoor environments. There are things that can be done by everyone to minimize the risk of infection."

Should I get a booster now or wait until the fall?

Health experts believe the current vaccines still work well to prevent severe illness and death. But their waning ability to prevent infections prompted the Food and Drug Administration to recommend that vaccine makers modify booster shots to target omicron strains such as BA.5. But federal health officials believe those still eligible for boosters should get them now, rather than waiting for new vaccines.

"Getting vaccinated now will not preclude you from getting a variant-specific vaccine later this fall or winter," Dr. Ashish Jha, the White House's COVID response coordinator, said last week. "This is not a trade-off."

See booster eligibility here.